IPAC2013 - List of Authors (Stoltz, P.)

Paper	Title	Page
MOPWA056	Spectra of Coherent Smith-Purcell Radiation Observed from Short Electron Bunches: Numerical and Experimental Studies	801
	F. Bakkali Taheri, G. Doucas, I.V. Konoplev, A. Reichold JAI, Oxford, United Kingdom H.L. Andrews LANL, Los Alamos, New Mexico, USA R. Bartolini Diamond, Oxfordshire, United Kingdom V. Bharadwaj, C.I. Clarke SLAC, Menlo Park, California, USA N. Delerue LAL, Orsay, France N. Fuster Martinez IFIC, Valencia, Spain J.D.A. Smith TXUK, Warrington, United Kingdom P. Stoltz Tech-X, Boulder, Colorado, USA
	Funding: This work performed [in part] under DOE Contract DE-AC02-7600515 There is a significant interest in the development of compact particle accelerators within research areas including X-ray and THz (T-ray) sources of radiation, particle physics and medical sciences. To support the progress in these areas, non-invasive, electron beam diagnostics that are capable of measuring a single femtosecond electron bunch are required. At the current stage such beam diagnostics for femtosecond-long electron bunches are still not available. The goal of the work presented is to understand the spectral characteristics of coherent Smith-Purcell radiation to enable its quick and reliable interpretation including the longitudinal profile reconstruction of electron bunches. The research presented comprises results from numerical modelling and experimental studies. Using the numerical data, we discuss the radiated spectra dependence on the electron bunch profile and analyse the results. We also discuss the experimental data and compare it with theoretical predictions.

MOPWO068	Simulating Electron Cloud Evolution using Modulated Dielectric Models	1043
	S.A. Veitzer, P. Stoltz Tech-X, Boulder, Colorado, USA
	Funding: This work was performed under the auspices of the Department of Energy as part of the ComPASS SCiDAC-2 project (DE-FC02-07ER41499), and the SCiDAC-3 project (DE-SC0008920) Electron clouds can pose a serious threat to accelerator performance, and understanding cloud buildup and the effectiveness of different mitigation techniques can provide cost-saving improvements in accelerator design and fabrication. Microwave diagnostics of electron clouds are a non-destructive way to measure cloud buildup, but it is very difficult to measure the cloud density from spectral signals alone. Modeling travelling-wave rf diagnostics is very hard because of the large range of spatial and temporal scales that must be resolved to simulate spectra. New numerical models have been used to generate synthetic spectra for electron clouds when the cloud density is not changing, and results have been compared to theoretical results. Here we use dielectric models to generate spectra for clouds that evolve over many bunch crossings. We first perform detailed simulations of cloud buildup using kinetic particle models, and then use an equivalent plasma dielectric model corresponding to this density, at a finer time resolution, to compute spectra. The stability and accuracy of dielectric models that spectra can be accurately determined in these very long timescale simulations.

TUPEA071	THz Bench Tests of a Slab-symmetric Dielectric Waveguide	1292
	F. Lemery, H. Panuganti, P. Piot Northern Illinois University, DeKalb, Illinois, USA D. Mihalcea, P. Piot Fermilab, Batavia, USA P. Stoltz Tech-X, Boulder, Colorado, USA
	Funding: This work is supported by DTRA contract HDTRA1-10-1-0051 and by the U.S. DOE contracts DE-FG02-08ER41532 and DE-AC02-07CH11359. Dielectric-lined waveguides (DLW) are becoming more popular for beam driven acceleration applications. An experiment to demonstrate beam-driven acceleration using a slab-symmetric dielectric-lined waveguide driven by a flat beam is in preparation at the Advanced Superconducting Test Accelerator (ASTA) at Fermilab. In this paper we characterize the structure using a THz pulse obtained from optical rectification using an amplified laser pulse. After propagation through the DLW structure, the THz pulse is analyzed using a Michelson interferometer and single-shot electro-optical imaging. Data for various gap size will be presented.

TUPEA072	Toward a Dielectric-Wakefield Energy Doubler at the Fermilab's Advanced Superconducting Test Accelerator	1295
	F. Lemery, D. Mihalcea, P. Piot, C.R. Prokop Northern Illinois University, DeKalb, Illinois, USA P. Piot, Y.-E. Sun Fermilab, Batavia, USA P. Stoltz Tech-X, Boulder, Colorado, USA
	Funding: This work is supported by DTRA contract HDTRA1-10-1-0051 and by the U.S. DOE contracts DE-FG02-08ER41532 and DE-AC02-07CH11359. The Advanced Superconducting Test Accelerator (ASTA), presently under construction at Fermilab, will produce high-charge (~<3 nC) electron bunches with energies ranging from 50 to eventually 750 MeV. The facility is based on a superconducting linac capable of producing up to 3000 bunches in 1-ms macropulses repeated at 5 Hz. In this paper we explore the use of a short dielectric-lined-waveguide (DLW) linac to significantly increase the bunch energy. The method consists in (1) using advanced phase space manipulation techniques to shape the beam distribution and enhance the transformer ratio, and (2) optimize the generation and acceleration of a low-charge witness bunches. Start-to-end simulations of the proposed concept are presented. This DLW module could also be used to test some aspects of a recently proposed concept for a multiuser short-wavelength free-electron laser utilizing a series of DLW linacs. C. Jing et al., “A Compact Soft X-ray Free-Electron Laser Facility based on a Dielectric Wakefield Accelerator”, Advanced Photon Source LS Note LS-332, Argonne National Laboratory (2012).

TUPEA073	Performances of VORPAL-GPU Slab-symmetric DLW	1298
	F. Lemery, K. Duffin, N. Karonis, D. Mihalcea, P. Piot, J. Winans Northern Illinois University, DeKalb, Illinois, USA P.J. Mullowney, P. Stoltz Tech-X, Boulder, Colorado, USA P. Piot Fermilab, Batavia, USA
	Funding: HDTRA1-10-1-0051, DOE(Grant No will be specified later) GPU-based computing has gained popularity in recent years due to its growing software support and greater processing capabilities than its CPU counterpart. GPU computing was recently added in the finite-difference time-domain program VORPAL. In this paper we carry electromagnetic simulations and optimization of a flat beam passing through a slab-symmetric dielectric-lined waveguide (DLW). We use this simulation model to explore the scaling of the GPU version of VORPAL on a new TOP1000-grade hybrid GPU/CPU computer cluster available at Northern Illinois University.

Paper

Title

Page

Spectra of Coherent Smith-Purcell Radiation Observed from Short Electron Bunches: Numerical and Experimental Studies

801

F. Bakkali Taheri, G. Doucas, I.V. Konoplev, A. Reichold
JAI, Oxford, United Kingdom
H.L. Andrews
LANL, Los Alamos, New Mexico, USA
R. Bartolini
Diamond, Oxfordshire, United Kingdom
V. Bharadwaj, C.I. Clarke
SLAC, Menlo Park, California, USA
N. Delerue
LAL, Orsay, France
N. Fuster Martinez
IFIC, Valencia, Spain
J.D.A. Smith
TXUK, Warrington, United Kingdom
P. Stoltz
Tech-X, Boulder, Colorado, USA

Funding: This work performed [in part] under DOE Contract DE-AC02-7600515
There is a significant interest in the development of compact particle accelerators within research areas including X-ray and THz (T-ray) sources of radiation, particle physics and medical sciences. To support the progress in these areas, non-invasive, electron beam diagnostics that are capable of measuring a single femtosecond electron bunch are required. At the current stage such beam diagnostics for femtosecond-long electron bunches are still not available. The goal of the work presented is to understand the spectral characteristics of coherent Smith-Purcell radiation to enable its quick and reliable interpretation including the longitudinal profile reconstruction of electron bunches. The research presented comprises results from numerical modelling and experimental studies. Using the numerical data, we discuss the radiated spectra dependence on the electron bunch profile and analyse the results. We also discuss the experimental data and compare it with theoretical predictions.

MOPWO068

Simulating Electron Cloud Evolution using Modulated Dielectric Models

1043

S.A. Veitzer, P. Stoltz
Tech-X, Boulder, Colorado, USA

Funding: This work was performed under the auspices of the Department of Energy as part of the ComPASS SCiDAC-2 project (DE-FC02-07ER41499), and the SCiDAC-3 project (DE-SC0008920)
Electron clouds can pose a serious threat to accelerator performance, and understanding cloud buildup and the effectiveness of different mitigation techniques can provide cost-saving improvements in accelerator design and fabrication. Microwave diagnostics of electron clouds are a non-destructive way to measure cloud buildup, but it is very difficult to measure the cloud density from spectral signals alone. Modeling travelling-wave rf diagnostics is very hard because of the large range of spatial and temporal scales that must be resolved to simulate spectra. New numerical models have been used to generate synthetic spectra for electron clouds when the cloud density is not changing, and results have been compared to theoretical results. Here we use dielectric models to generate spectra for clouds that evolve over many bunch crossings. We first perform detailed simulations of cloud buildup using kinetic particle models, and then use an equivalent plasma dielectric model corresponding to this density, at a finer time resolution, to compute spectra. The stability and accuracy of dielectric models that spectra can be accurately determined in these very long timescale simulations.

TUPEA071

THz Bench Tests of a Slab-symmetric Dielectric Waveguide

1292

F. Lemery, H. Panuganti, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
D. Mihalcea, P. Piot
Fermilab, Batavia, USA
P. Stoltz
Tech-X, Boulder, Colorado, USA

Funding: This work is supported by DTRA contract HDTRA1-10-1-0051 and by the U.S. DOE contracts DE-FG02-08ER41532 and DE-AC02-07CH11359.
Dielectric-lined waveguides (DLW) are becoming more popular for beam driven acceleration applications. An experiment to demonstrate beam-driven acceleration using a slab-symmetric dielectric-lined waveguide driven by a flat beam is in preparation at the Advanced Superconducting Test Accelerator (ASTA) at Fermilab. In this paper we characterize the structure using a THz pulse obtained from optical rectification using an amplified laser pulse. After propagation through the DLW structure, the THz pulse is analyzed using a Michelson interferometer and single-shot electro-optical imaging. Data for various gap size will be presented.

TUPEA072

Toward a Dielectric-Wakefield Energy Doubler at the Fermilab's Advanced Superconducting Test Accelerator

1295

F. Lemery, D. Mihalcea, P. Piot, C.R. Prokop
Northern Illinois University, DeKalb, Illinois, USA
P. Piot, Y.-E. Sun
Fermilab, Batavia, USA
P. Stoltz
Tech-X, Boulder, Colorado, USA

Funding: This work is supported by DTRA contract HDTRA1-10-1-0051 and by the U.S. DOE contracts DE-FG02-08ER41532 and DE-AC02-07CH11359.
The Advanced Superconducting Test Accelerator (ASTA), presently under construction at Fermilab, will produce high-charge (~<3 nC) electron bunches with energies ranging from 50 to eventually 750 MeV. The facility is based on a superconducting linac capable of producing up to 3000 bunches in 1-ms macropulses repeated at 5 Hz. In this paper we explore the use of a short dielectric-lined-waveguide (DLW) linac to significantly increase the bunch energy. The method consists in (1) using advanced phase space manipulation techniques to shape the beam distribution and enhance the transformer ratio, and (2) optimize the generation and acceleration of a low-charge witness bunches. Start-to-end simulations of the proposed concept are presented. This DLW module could also be used to test some aspects of a recently proposed concept for a multiuser short-wavelength free-electron laser utilizing a series of DLW linacs*.
* C. Jing et al., “A Compact Soft X-ray Free-Electron Laser Facility based on a Dielectric Wakefield Accelerator”, Advanced Photon Source LS Note LS-332, Argonne National Laboratory (2012).

TUPEA073

Performances of VORPAL-GPU Slab-symmetric DLW

1298

F. Lemery, K. Duffin, N. Karonis, D. Mihalcea, P. Piot, J. Winans
Northern Illinois University, DeKalb, Illinois, USA
P.J. Mullowney, P. Stoltz
Tech-X, Boulder, Colorado, USA
P. Piot
Fermilab, Batavia, USA

Funding: HDTRA1-10-1-0051, DOE(Grant No will be specified later)
GPU-based computing has gained popularity in recent years due to its growing software support and greater processing capabilities than its CPU counterpart. GPU computing was recently added in the finite-difference time-domain program VORPAL. In this paper we carry electromagnetic simulations and optimization of a flat beam passing through a slab-symmetric dielectric-lined waveguide (DLW). We use this simulation model to explore the scaling of the GPU version of VORPAL on a new TOP1000-grade hybrid GPU/CPU computer cluster available at Northern Illinois University.